1. Field of the Invention
This invention relates to a device for rapidly defrosting a refrigerator compartment in accordance with the introductory part of the main claim.
2. Description of the Related Art
As is well known, devices for rapidly defrosting a refrigerator compartment, for example the freezer compartment, have been commercially available for some time. These devices comprise for example one or more armoured resistance elements associated with the evaporator or with its hairpin coils and, in the case of a forced-air refrigerator, with the usual collection member (tray) for the water resulting from defrosting. These resistance elements have a high thermal power which however being localized does not allow properly ample and rapid defrosting of the refrigerator compartment. Moreover, to achieve rapid defrosting, said resistance elements would have to be present in a considerable number on the evaporator. Such a solution is however industrially unattainable.
To the aforegoing it must be added that, as is well known, each refrigerator compartment consists of a substantially parallelepiped cell, for example of aluminum, on the outside of which there is positioned the evaporator hairpin coil which during the operating cycle reduces the temperature within the cell to below 0.degree. C. To prevent ice forming on the cell interior with the passage of time (due to the moisture in the air) and depositing on the walls to reduce the cell efficiency, said refrigeration cells are provided externally with electrical resistance elements which can also be activated manually when required. These resistance elements consist of a resistive wire wound on a polyester support, the whole being covered with a PVC sheath which is inserted into a metal tube extending substantially parallel to the hairpin coil of the evaporator. The latter and said tube are embedded in a layer of foamed material which wraps the cell.
To prevent damage to the foamed layer by overheating of said resistance elements when these are powered to implement defrosting, one or more protection devices must be provided in the power circuit of said resistance elements, for example thermostats which interrupt said power when the temperature of the resistance elements reaches a predetermined value beyond which permanent damage can occur to the foamed material, with resultant diminution in its insulating capacity. Such a circuit therefore becomes considerably complicated with consequent high manufacturing costs.